US2628199A

US2628199A - Tarnish remover

Info

Publication number: US2628199A
Application number: US134360A
Authority: US
Inventors: Frederick A Lowenheim
Original assignee: Individual
Current assignee: Individual
Priority date: 1949-12-21
Filing date: 1949-12-21
Publication date: 1953-02-10
Anticipated expiration: 1970-02-10

Description

I Patented Feb. 10, 1953 r Frederick A. Lowenheim, Plainfleld, N'- J.

No Drawing- Application December 21, 1949,

a claim. (oi. ass-4m 1 This invention relates to a comgsgiolriikfofig mmoving tarng' h and MM and e V e 1 1 meta 5 aces withoilr'iffackin the metal;

cleani such in silv silver p ate, 9 21:

, brass, bronze and other com r alloys.

its essence, the compositifidn'sistsessentially of an acid having a pK' in the range of 1 to 5 and thiourea. By the expression "p is meant the negative logarithm of the dissociation constant, K. While not limited thereto, it is intended to provide the composition in the form oi a dry powder mixture and to require a purchaser, before using the same, to add water to the mixture, the amount of water to depend upon the character of the impurities to be removed from the metal surfaces. T,he invention, however, also IIIH 8. com 0| 0:

The ingredients of the compositions are water-soluble.

Generally speaking, the dry mixture comprises a normally solid acid having a pK in the range of 1 to 5 and thiourea. Ihe amount otthiourea should exceed the amount of acid with the former comprising about 3 to 5 parts 'by weight, 2

, in, or, as is preferable, by adding a wetting agent in solid form to the dry powder mixture.

As examples of solid acids having a pK of 1 to 5, there may be mentio'ned citric, o c, tartaric, phthalic, and succinic acids. as is ter-insoluble c u l- I They are also a 0 ac cdspK oflessthan 1 are too corrosive for the purpose intended, while acids having a pK greater than 5 are inoperable. The preferred acids are the aliphatic. polybaslc. hydroxy acids like citric and tartaric, which are non-toxic and non-irritating to the skin.

Besides thiourea, simple alkyl derivatives thereof such as methyl or ethyl thiourea are also u sgf 1 i1 These derivatives are contemplated by the expression "thiourea.

As wetting agents there may be mentioned such materia 1 alcohol derivatives, salts of substituted aromatic suliouicacids, sulfonated fatty alcohols, sulfonated vegetable oil, highly sulfonated fatty acid esters, diglycol stearate, or-

ci wic do not form More particularly, It relates 55 a composition for" M ganic acid esters ofdiethylene glycol, N-alkylol fatty amides, w :alene esters, complex amides of fatty ac g er a p a 10 and mixed aliphatic-aromatic quaternary ammonium hal- 5 ides, higher aliphatic amines, etc.

As an example of adry mixture, 200 parts of powdered thlourea and 50 parts of powdered citric unaware mixed, and then 8 parts of a powdered commercial l'auryl alcohol derivative was added thereto." This mixture was dissolved in water, the amount of which is not critical, and was foundto be effective to remove the'tarnish from silver, copper and copper alloys. Another powder mixture containing 50 g. of thiourea, 10 g. of citric acid, and l g. of the above mentioned wetting agent was added to 1 liter of water. This solution was also found to be efiectiye for removin tarnish from silver, co er and copper alloy articles merely 5 di ping.

For impurities that are Hficult to remove, the action of the composition may be aided by incorporating an abrasive agent either to the dry mixture or to the aqueous solution of the same and then employing a slight rubbing action in conjunction with the immersion treatment. Any conventional abrasive such as infusorial earth, diatomaceous earth, etc. is useful for this purpose. As an example of a dry powder containing an abrasive, a mixture of 400 parts of thiourea, parts of citric acid, 10 parts of wetting agent and 100 parts of diatomaceous earth was prepared. While desirable in some cases, an abrasive is not always necessary, as stubborn impurities can often be removed by treating them with a non-abrasive-containing composition to which just enough water has been added to moisten the powder without dissolving it. In such cases, only very gentle rubbing may be necessary to efiect the desired result.

It may be noted that the dry mixtures disclosed herein possess a desirable advantage in being packageable in dry form, in distinction to a paste or liquid. The mixtures are not corrosive to ordinary packing materials, nor are the aqueous solutions of the same corrosive in respect to the metals that are to be cleaned.

As indicated, other compositions comprising aqueous mixtures may be useful. These prefer ably comprise acids that are normall li uid, such as acetic formic, maleic and hgsphnric, all of which have a pK of 1 to 5. Like the solid acids, they are water-soluble, stable, non-oxidizing, and do not form water-insoluble compounds with copper or silver. Compositions containing these acids may be formed as described above,

the thiourea going into solution. in the acid. Preferably a liquid wetting agent is used. As will be apparent, aqueous compositions for immediate use may also be prepared from the solid acids.

In the light of the foregoing description, the iollowing is claimed:

1. A cleaning composition for silver-; and copper-containing metal surfaces consisting 'essentially of 1 part by weight of an acid having apKintherange oi 1to5 and about3 to 5partsby weight of thiourea, said acid being watersoiuble, stable, non-oxidizing, and forming no water-insoluble compounds with copper or'silver.

alloys comprising a dry powder mixture consist- 2. A cleaner for silver, copper, and copper alloys comprising a dry powder mixture consisting essentially of 1 part by weight of a solid acid having a mi in the range oi. 1 to 5 and'about 3 to 5 parts by weight of thiourea, said acid being water-soluble, stable, non-oiddizing, and forming no water-insoluble compounds with copper or silver, said mixture being adapted to be dissolved in water before use.

3. A cleaner for silver, copper, and copper alloys comprising a dry powder mixture consistin essentially of 1 part by weight of an aliphatic, polybasic, solid acid having a pK in the range of 1 to 5 and about 4 parts by weight of thiourea, said acid being water-soluble, stable, non-oxidizing, and forming no water-insoluble compounds with cooper or silver, said mixture being adapted to be at least partially treated with water before use.

"weight of an organic acid having a pK in the range of 1 to 5 and about 3 to 5 parts by weight of thiourea, said acid being water-soluble, stable, non-oxidizing, and forming no water-insoluble compounds with copper or silver.

8..A'.cleaner-for silver, copper, and copper -ing essentially oi'l'part by weight of a solid orgahic'acid having a pK in the range of 1 to 5 and about 3 to 5 parts by weight of thiourea, said 4. A cleaner according to claim 3 in which the acid being water-soluble, stable, non-oxidizing, and forming no water-insoluble compounds with copper or silver, said mixture being adapted to be dissolved in water before use.

, FREDERICK A. LOWENHEIM.

Name Date 1,608,622 Schmidt et al Nov. 30, 1926 2,071,966 Bolton Feb. 23, 1937 2,383,800. Johnson Aug. 28, 1945 2,393,866 Wassell Jan. 29, 1946 2,485,529 Cardweil et al Oct. 18, 1949

Claims

1. A CLEANING COMPOSITION FOR SILVER- AND COPPER-CONTAINING METAL SURFACES CONSISTING ESSENTIALLY OF 1 PART BY WEIGHT OF AN ACID HAVING A PK IN THE RANGE OF 1 TO 5 AND ABOUT 3 TO 5 PARTS BY WEIGHT OF THIOUREA, SAID ACID BEING WATERSOLUBLE, STABLE, NON-OXIDIZING, AND FORMING NO WATER-INSOLUBLE COMPOUNDS WITH COPPER OR SILVER.